(function(win, lib) {

    var doc = win.document;
  
    var docEl = doc.documentElement;
  
    var metaEl = doc.querySelector('meta[name="viewport"]');
  
    var flexibleEl = doc.querySelector('meta[name="flexible"]');
  
    var dpr = 0;
  
    var scale = 0;
  
    var tid;
  
    var flexible = lib.flexible || (lib.flexible = {});
  
    let rem = 0;
  
    if (metaEl) {
  
        console.warn('将根据已有的meta标签来设置缩放比例');
  
        var match = metaEl.getAttribute('content').match(/initial\-scale=([\d\.]+)/);
  
        if (match) {
  
            scale = parseFloat(match[1]);
  
            dpr = parseInt(1 / scale);
  
        }
  
    } else if (flexibleEl) {
  
        var content = flexibleEl.getAttribute('content');
  
        if (content) {
  
            var initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
  
            var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/);
  
            if (initialDpr) {
  
                dpr = parseFloat(initialDpr[1]);
  
                scale = parseFloat((1 / dpr).toFixed(2));
  
            }
  
            if (maximumDpr) {
  
                dpr = parseFloat(maximumDpr[1]);
  
                scale = parseFloat((1 / dpr).toFixed(2));
  
            }
  
        }
  
    }
  
    if (!dpr && !scale) {
  
        var isAndroid = win.navigator.appVersion.match(/android/gi);
  
        var isIPhone = win.navigator.appVersion.match(/iphone/gi);
  
        var devicePixelRatio = win.devicePixelRatio;
  
        if (isIPhone) {
  
            // iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案
  
            if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
  
                dpr = 3;
  
            } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)){
  
                dpr = 2;
  
            } else {
  
                dpr = 1;
  
            }
  
        } else {
  
            // 其他设备下，仍旧使用1倍的方案
  
            dpr = 1;
  
        }
  
        scale = 1 / dpr;
  
    }
  
    docEl.setAttribute('data-dpr', dpr);
  
    if (!metaEl) {
  
        metaEl = doc.createElement('meta');
  
        metaEl.setAttribute('name', 'viewport');
  
        metaEl.setAttribute('content', 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no');
  
        if (docEl.firstElementChild) {
  
            docEl.firstElementChild.appendChild(metaEl);
  
        } else {
  
            var wrap = doc.createElement('div');
  
            wrap.appendChild(metaEl);
  
            doc.write(wrap.innerHTML);
  
        }
  
    }
  
    function refreshRem(){
  
        var width = docEl.getBoundingClientRect().width;
  
        //根据项目的适配范围设置
  
        if (width / dpr < 1400) {
  
            width = 1400 * dpr;
  
        } else if (width / dpr > 2560) {
  
            width = 2560 * dpr;
  
        }
  
        //根据设计稿宽度设置1rem代表多少像素，
  
        // rem = (width / 24) ;
  
        // docEl.style.fontSize = rem + 'px';
  
        // flexible.rem = win.rem = rem;
  
        var rem = width / 74;
  
        docEl.style.fontSize = rem + 'px';
  
        flexible.rem = win.rem = rem;
  
    }
  
    win.addEventListener('resize', function() {
  
        clearTimeout(tid);
  
        tid = setTimeout(refreshRem, 300);
  
    }, false);
  
    win.addEventListener('pageshow', function(e) {
  
        if (e.persisted) {
  
            clearTimeout(tid);
  
            tid = setTimeout(refreshRem, 300);
  
        }
  
    }, false);
  
    if (doc.readyState === 'complete') {
  
        doc.body.style.fontSize = 12 * dpr + 'px';
  
    } else {
  
        doc.addEventListener('DOMContentLoaded', function(e) {
  
            doc.body.style.fontSize = 12 * dpr + 'px';
  
        }, false);
  
    }
  
  
   
  
    refreshRem();
  
    flexible.dpr = win.dpr = dpr;
  
    flexible.refreshRem = refreshRem;
  
    flexible.rem2px = function(d) {
  
        var val = parseFloat(d) * this.rem;
  
        if (typeof d === 'string' && d.match(/rem$/)) {
  
            val += 'px';
  
        }
  
        return val;
  
    }
  
    flexible.px2rem = function(d) {
  
        var val = parseFloat(d) / this.rem;
  
        if (typeof d === 'string' && d.match(/px$/)) {
  
            val += 'rem';
  
        }
  
        return val;
  
    }
  
  })(window, window['lib'] || (window['lib'] = {}));
  
  